זמנים
הלכות עירובין
פרק א

Halacha

הלכה א
חָצֵר שֶׁיֵּשׁ בָּהּ שְׁכֵנִים הַרְבֵּה כָּל אֶחָד מֵהֶם בְּבַיִת לְעַצְמוֹ דִּין תּוֹרָה הוּא שֶׁיִּהְיוּ כֻּלָּן מֻתָּרִין לְטַלְטֵל בְּכָל הֶחָצֵר וּמִבָּתִּים לֶחָצֵר וּמֵהֶחָצֵר לַבָּתִּים מִפְּנֵי שֶׁכָּל הֶחָצֵר רְשׁוּת הַיָּחִיד אַחַת וּמֻתָּר לְטַלְטֵל בְּכֻלָּהּ. וְכֵן הַדִּין בְּמָבוֹי שֶׁיֵּשׁ לוֹ לֶחִי אוֹ קוֹרָה שֶׁיִּהְיוּ כָּל בְּנֵי הַמָּבוֹי מֻתָּרִים לְטַלְטֵל בְּכֻלּוֹ וּמֵחֲצֵרוֹת לַמָּבוֹי וּמִמָּבוֹי לַחֲצֵרוֹת שֶׁכָּל הַמָּבוֹי רְשׁוּת הַיָּחִיד הוּא. וְכֵן הַדִּין בִּמְדִינָה שֶׁהִיא מֻקֶּפֶת חוֹמָה גְּבוֹהָה עֲשָׂרָה טְפָחִים שֶׁיֵּשׁ לָהּ דְּלָתוֹת וְנִנְעָלוֹת בַּלַּיְלָה שֶׁכֻּלָּהּ רְשׁוּת הַיָּחִיד הִיא. זֶה הוּא דִּין תּוֹרָה:
כסף משנה
1.
According to Torah law, when there are several neighbors dwelling in a courtyard, each in his private home, they are all permitted to carry within the entire courtyard, from the homes to the courtyard, and from the courtyard to the homes, because the entire courtyard is a private domain1Included in this private domain are all the houses located in the courtyard. and it is permitted to carry within it in its entirety.
Similarly, regarding a lane that has a pole [positioned at its entrance] or a beam positioned [above it],2See Hilchot Shabbat 17:2,9. all the inhabitants of the lane are permitted to carry3The Maggid Mishneh notes that according to Torah law [op. cit.; see also the Rambam's Commentary on the Mishnah (Eruvin 1:2) ], it is permitted to carry within a lane, even though it does not have a pole or a beam. Nevertheless, it is then considered a makom patur and not a private domain. in the entire [lane], and from the courtyards to the lane,4As obvious from Hilchot Shabbat 17:2,8, a lane is an area enclosed by three walls and into which several courtyards open. and from the lane to the courtyards, for the entire lane is a private domain.
Similarly, all [the area within] a city that is surrounded by a wall that is [at least] ten handbreadths high and has gates that are locked at night5Based on the Rambam's statements in Hilchot Shabbat 17:10, the Maggid Mishneh and the Radbaz (Vol. V, Responsum 1508) state that the gates of the city need not actually be locked at night; it is sufficient that they are able to be locked. is a private domain. This is the law of the Torah.

הלכה ב
אֲבָל מִדִּבְרֵי סוֹפְרִים אָסוּר לִשְׁכֵנִים לְטַלְטֵל בִּרְשׁוּת הַיָּחִיד שֶׁיֵּשׁ בָּהּ חֲלוּקָה בְּדִיּוּרִין עַד שֶׁיְּעָרְבוּ כָּל הַשְּׁכֵנִים כֻּלָּן מֵעֶרֶב שַׁבָּת. אֶחָד חָצֵר וְאֶחָד מָבוֹי וְאֶחָד הַמְּדִינָה. וְדָבָר זֶה תַּקָּנַת שְׁלֹמֹה וּבֵית דִּינוֹ:
כסף משנה
2.
Nevertheless, according to Rabbinic decree, it is forbidden for the neighbors to carry within a private domain that is divided into different dwellings, unless all the inhabitants join together in an eruv before the commencement of the Sabbath.
This [restriction] applies to courtyards, lanes, and cities. It was instituted by [King] Solomon and his court.6Eruvin 21b states that when King Solomon instituted the requirement for eruvin, a heavenly voice resounded, quoting Proverbs 23:15: "My son, if your heart is wise, My heart will also rejoice."
Sefer HaMitzvot Gadol asks why this requirement was not instituted in an earlier time, and quotes a letter of Rav Hai Gaon that explains that prior to King Solomon's era, the Jews were very heavily involved in wars (to conquer the land of Canaan, and then to protect themselves from the Philistines and others). It was not until King Solomon's time that the land was blessed with peace. Since an army camp is not obligated to heed the restrictions of eruvin (Hilchot Melachim 6:13), the practice was not instituted until the age when peace became the norm in Eretz Yisrael.

הלכה ג
וְכֵן יוֹשְׁבֵי אֹהָלִים אוֹ סֻכּוֹת אוֹ מַחֲנֶה שֶׁהִקִּיפוּהוּ מְחִצָּה אֵין מְטַלְטְלִין מֵאֹהֶל לְאֹהֶל עַד שֶׁיְּעָרְבוּ כֻּלָּן. אֲבָל שַׁיָּרָא שֶׁהִקִּיפָה מְחִצָּה אֵין צְרִיכִין לְעָרֵב אֶלָּא מוֹצִיאִין מֵאֹהֶל לְאֹהֶל בְּלֹא עֵרוּב לְפִי שֶׁהֵן כֻּלָּן מְעֹרָבִין וְאֵין אוֹתָן אֹהָלִים קְבוּעִין לָהֶן:
כסף משנה
3.
Similarly, people who dwell in tents,7These all refer to dwellings that are intended to endure for an extended period (Maggid Mishneh). in booths, or in an encampment8This refers to a camp other than an army camp, as mentioned in Note 6. that is surrounded by a partition may not carry from tent to tent until they make an eruv. In contrast, [the members of] a caravan [who surround their encampment] with a partition are not required to [join in] an eruv.9The Rashba and the Ritba differ from the Rambam on this point and maintain that the travelers in a caravan are required to establish an eruv, and the dwellers of a camp are not. Note the explanation of their difference of opinion in the Be'ur Halachah 366. They may transfer articles from tent to tent without an eruv, for [the very nature of their circumstance] is considered to be an eruv, since these are not long-lasting dwellings.10As mentioned in Halachah 2, the obligation to establish an eruv was instituted to apply to people living in separate dwellings in a single domain. Since these structures are not enduring by nature, the people are not considered to be living in separate dwellings, and the restriction against carrying is therefore not instituted. (See Mishnah Berurah 366:12.)

הלכה ד
וּמִפְּנֵי מָה תִּקֵּן שְׁלֹמֹה דָּבָר זֶה. כְּדֵי שֶׁלֹּא יִטְעוּ הָעָם וְיֹאמְרוּ כְּשֵׁם שֶׁמֻּתָּר לְהוֹצִיא מִן הַחֲצֵרוֹת לִרְחוֹבוֹת הַמְּדִינָה וּשְׁוָקֶיהָ וּלְהַכְנִיס מֵהֶם לַחֲצֵרוֹת כָּךְ מֻתָּר לְהוֹצִיא מִן הַמְּדִינָה לַשָּׂדֶה וּלְהַכְנִיס מִן הַשָּׂדֶה לַמְּדִינָה. וְיַחְשְׁבוּ שֶׁהַשְּׁוָקִים וְהָרְחוֹבוֹת הוֹאִיל וְהֵן רְשׁוּת לַכּל הֲרֵי הֵן כְּשָׂדוֹת וּכְמִדְבָּרוֹת וְיֹאמְרוּ שֶׁהַחֲצֵרוֹת בִּלְבַד הֵן רְשׁוּת הַיָּחִיד וִידַמּוּ שֶׁאֵין הַהוֹצָאָה מְלָאכָה וְשֶׁמֻּתָּר לְהוֹצִיא וּלְהַכְנִיס מֵרְשׁוּת הַיָּחִיד לִרְשׁוּת הָרַבִּים:
כסף משנה
4.
Why did [King] Solomon institute this [restriction]? So that the common people would not err and say, "Just as it is permitted to transfer articles from the courtyards to the streets of a city and its marketplaces, and to bring articles in [from these domains] to a courtyard, it is permitted to take articles from the city to the fields and from the fields to the city."
[Moreover, they would operate under the mistaken] impression that the marketplaces and streets - since they are the public domain - are like fields and deserts.11See Hilchot Shabbat 14:1 and notes, which discuss the Rambam's opinion that deserts are a public domain. [This would lead them to a further error, causing them to] say that only a courtyard is a private domain,12The Lechem Mishneh comments that according to this logic, it would be unnecessary to forbid taking articles out from homes to a courtyard. He continues, explaining that this restriction is also necessary so that children who are knowledgeable only about what goes on in their homes and the adjacent courtyard will be aware of the obligation of making an eruv. and they would think that there is no prohibition against the transfer of articles, and that it is permitted to transfer articles from a private domain to a public domain [and from a public domain to a private domain].

הלכה ה
לְפִיכָךְ תִּקֵּן שֶׁכָּל רְשׁוּת הַיָּחִיד שֶׁתֶּחֱלַּק בְּדִיּוּרִין וְיֹאחַז כָּל אֶחָד וְאֶחָד בָּהּ רְשׁוּת לְעַצְמוֹ וְיִשָּׁאֵר מִמֶּנָּה מָקוֹם בִּרְשׁוּת כֻּלָּן וְיַד כֻּלָּן שָׁוָה בּוֹ כְּגוֹן חָצֵר לַבָּתִּים. שֶׁנַּחְשֹׁב אוֹתוֹ הַמָּקוֹם שֶׁיַּד כֻּלָּן שָׁוָה בּוֹ כְּאִלּוּ הוּא רְשׁוּת לָרַבִּים. וְנֶחְשָׁב כָּל מָקוֹם וּמָקוֹם שֶׁאָחַז כָּל אֶחָד מִן הַשְּׁכֵנִים וְחִלְּקוֹ לְעַצְמוֹ שֶׁהוּא בִּלְבַד רְשׁוּת הַיָּחִיד. וְיִהְיֶה אָסוּר לְהוֹצִיא מֵרְשׁוּת שֶׁחָלַק לְעַצְמוֹ לִרְשׁוּת שֶׁיַּד כֻּלָּם שָׁוָה בּוֹ. כְּמוֹ שֶׁאֵין מוֹצִיאִין מֵרְשׁוּת הַיָּחִיד לִרְשׁוּת הָרַבִּים. אֶלָּא יִשְׁתַּמֵּשׁ כָּל אֶחָד בָּרְשׁוּת שֶׁחָלַק לְעַצְמוֹ בִּלְבַד עַד שֶׁיְּעָרְבוּ כֻּלָּן אַף עַל פִּי שֶׁהַכּל רְשׁוּת הַיָּחִיד:
כסף משנה
5.
Therefore, [King Solomon] instituted [the following rules]: Whenever a private domain is divided into separate dwelling units that are considered the private property of the individuals, and an area remains that is the joint property of all individuals and all share in it equally - e.g., a courtyard with houses13In this halachah, the Rambam is clarifying that the distinctions between different domains with regard to the laws of ownership could create confusion with regard to the domains of the Sabbath. As a safeguard, King Solomon instituted the laws of eruvin.
The Tosafot Yom Tov (Eruvin 7:1) maintains that it is the Rambam's view that a group of houses adjacent to each other without a courtyard does not require an eruv; that is necessary only when there is jointly owned property in the private domain. The Tosafot Yom Tov himself differs from this position and requires an eruv in such a situation. In practice, it is not customary to require an eruv unless there is jointly owned property in the domain.
that open onto it - the area that is jointly owned is considered as a public domain. Similarly, every place that one of the neighbors owns as his private property and treats as his individual holding shall be considered as a private domain.
It is thus forbidden to transfer an article from a person's private property to the area that is owned jointly, just as it is forbidden to transfer from a private domain into the public domain. Instead, every person should contain his activities within his own property, unless an eruv is established, although [according to the Torah] the entire area is one private domain.

הלכה ו
וּמַה הוּא הָעֵרוּב הַזֶּה. הוּא שֶׁיִּתְעָרְבוּ בְּמַאֲכָל אֶחָד שֶׁמַּנִּיחִין אוֹתוֹ מֵעֶרֶב שַׁבָּת. כְּלוֹמַר שֶׁכֻּלָּנוּ מְעֹרָבִין וְאֹכֶל אֶחָד לְכֻלָּנוּ וְאֵין כָּל אֶחָד מִמֶּנּוּ חוֹלֵק רְשׁוּת מֵחֲבֵרוֹ אֶלָּא כְּשֵׁם שֶׁיַּד כֻּלָּנוּ שָׁוָה בְּמָקוֹם זֶה שֶׁנִּשְׁאַר לְכֻלָּנוּ כָּךְ יַד כֻּלָּנוּ שָׁוָה בְּכָל מָקוֹם שֶׁיֹּאחֵז כָּל אֶחָד לְעַצְמוֹ וַהֲרֵי כֻּלָּנוּ רְשׁוּת אֶחָד. וּבַמַּעֲשֶׂה הַזֶּה לֹא יָבוֹאוּ לִטְעוֹת וּלְדַמּוֹת שֶׁמֻּתָּר לְהוֹצִיא וּלְהַכְנִיס מֵרְשׁוּת הַיָּחִיד לִרְשׁוּת הָרַבִּים:
כסף משנה
6.
What is meant by an eruv? That all the individuals will join together in one [collection of] food before the commencement of the Sabbath. This serves as a declaration that they have all joined together and share food as one; none of them has [totally] private property. Instead, just as the jointly-owned area is the property of all, so too, everyone shares in the property that is privately owned. They are all joined in one domain.
[Performing] this act will prevent them from erring and thinking that it is permitted to transfer articles between a private domain and the public domain.

הלכה ז
הָעֵרוּב שֶׁעוֹשִׂים בְּנֵי הֶחָצֵר זֶה עִם זֶה הוּא הַנִּקְרָא עֵרוּבֵי חֲצֵרוֹת. וְשֶׁעוֹשִׂין אַנְשֵׁי מָבוֹי זֶה עִם זֶה אוֹ כָּל בְּנֵי הַמְּדִינָה הוּא הַנִּקְרָא שִׁתּוּף:
כסף משנה
7.
The eruv that the inhabitants of a courtyard make among themselves is referred to as eruvei chatzerot [the joining of the areas of courtyards]. [The joining together of] the inhabitants of a lane or of a city is referred to as shituf, [partnership].

הלכה ח
אֵין מְעָרְבִין בַּחֲצֵרוֹת אֶלָּא בְּפַת שְׁלֵמָה בִּלְבַד. אֲפִלּוּ כִּכַּר מַאֲפֶה סְאָה וְהִיא פְּרוּסָה אֵין מְעָרְבִין בָּהּ. הָיְתָה שְׁלֵמָה וְהִיא כְּאִיסָר מְעָרְבִין בָּהּ. וּכְשֵׁם שֶׁמְּעָרְבִין בְּפַת תְּבוּאָה כָּךְ מְעָרְבִין בְּפַת אֹרֶז וּבְפַת עֲדָשִׁים אֲבָל לֹא בְּפַת דֹּחַן. וְשִׁתּוּף בֵּין בְּפַת בֵּין בִּשְׁאָר אֳכָלִים. בְּכָל אֹכֶל מִשְׁתַּתְּפִין חוּץ מִן הַמַּיִם בִּפְנֵי עַצְמָן אוֹ מֶלַח בִּפְנֵי עַצְמוֹ. וְכֵן כְּמֵהִין וּפִטְרִיּוֹת אֵין מִשְׁתַּתְּפִין בָּהֶן שֶׁאֵינָן חֲשׁוּבִין כָּאֳכָלִים. עֵרֵב מַיִם עִם מֶלַח נַעֲשָׂה כְּמוּרְיָס וּמִשְׁתַּתְּפִין:
כסף משנה
8.
An eruv [joining together] the inhabitants of a courtyard may not be made with anything other than a whole loaf of bread.14Eruvin 81a states that this law was instituted to prevent quarrels among neighbors that might arise if one gave a whole loaf and one gave only a portion of a loaf. As stated in Halachah 16, every family in the courtyard gives a whole loaf. (See the notes on that halachah.) The Shulchan Aruch (Orach Chayim 366:7) states, however, that if an eruv is established by one person on behalf of others, without collecting flour or loaves of bread from the other inhabitants of the courtyard, it is possible to use a loaf that is not whole. Even if a loaf of bread is a se'ah15A large measure of grain, approximately 8 kilogram in contemporary measure. in size, but it is sliced, it may not be used for an eruv. If it is whole, even if it is as small as an isar,16A small Italian silver coin, weighing four barley corns (Hilchot Shekalim 1:3). it may be used for an eruv.17From the Rambam's wording, it would appear that there is no minimum measure required for the size of the loaf; as long as it is whole, it is sufficient, regardless of how many people dwell in the courtyard. Rav Moshe HaCohen and others differ, interpreting Eruvin 80b as requiring the loaf to be large enough to include a measure the size of a dried fig for each of the inhabitants (as the Rambam states in the following halachah regarding a shituf). It is Rav Moshe HaCohen's view that is accepted by the Shulchan Aruch (Orach Chayim 366:6, 368:3).
Just as an eruv may be made using a loaf of bread made from grain,18I.e., wheat, barley, spelt, oats, and rye. so too, may it be made with a loaf of bread made from rice19Based on the Rambam's Commentary on the Mishnah (Sh'vi'it 2:7), we have translated אורז as rice, and דוחן as millet. There are, however, different opinions concerning this matter. (See Magen Avraham 208:9; Turei Zahav 208:11.) or lentils. A loaf of bread made from millet, by contrast, may not be used.20For it is not common to make bread from millet.
The shituf [for a lane or for a city, by contrast, may be made using] either bread or other foods.21Rashi (Eruvin 71b) explains the difference between the eruv established in a courtyard and the shituf established in a lane as follows: An eruv is necessary in order to consider all of the dwellings as the mutually-owned property of all the members of the courtyard. Since the establishment of a location as a dwelling is a significant halachic act, it is necessary to use a significant food, bread. In contrast, the shituf joining together different courtyards is a far looser arrangement. Hence, other foods are also acceptable. For we may use any food for a shituf, with the exception of water and salt. Similarly, mushrooms and truffles may not be used for a shituf, because they are not considered to be foods.22In his Commentary on the Mishnah (Eruvin 3:1), the Rambam explains that mushrooms and truffles are a very base type of food. Hence, they are not considered acceptable.
In his gloss on the Shulchan Aruch (Orach Chayim 386:5), the Vilna Gaon writes that the exclusion does not apply to cooked mushrooms and truffles, for they are considered foods of high quality. Sefer HaKovetz differs and refutes all the proofs brought by the Vilna Gaon.

[The restriction against using water and salt applies only] when they are set aside as separate entities. If one mixes water and salt, this is considered to be brine, and may be used for a shituf.23By themselves, these are considered to be fit to prepare food, but not to be foods themselves (Rambam's Commentary on the Mishnah, loc. cit.). When mixed together as brine, they are suitable as a dip.
When quoting this ruling, the Shulchan Aruch (Orach Chayim 386:5) mentions the opinion of Tosafot (loc. cit.) that the brine must also be mixed with oil. Without this, the brine is unfit for use as a dip.

הלכה ט
וְכַמָּה שִׁעוּר הָאֹכֶל שֶׁמִּשְׁתַּתְּפִין בּוֹ. כִּגְרוֹגֶרֶת לְכָל אֶחָד וְאֶחָד מִבְּנֵי הַמָּבוֹי אוֹ מִבְּנֵי הַמְּדִינָה. וְהוּא שֶׁיִּהְיוּ שְׁמוֹנֶה עֶשְׂרֵה אוֹ פָּחוֹת. אֲבָל אִם הָיוּ מְרֻבִּים עַל זֶה שִׁעוּרוֹ שְׁתֵּי סְעֻדּוֹת שֶׁהֵן כִּשְׁמוֹנֶה עֶשְׂרֵה גְּרוֹגָרוֹת שֶׁהֵן כְּשֵׁשׁ בֵּיצִים בֵּינוֹנִיּוֹת. אֲפִלּוּ הָיוּ הַמִּשְׁתַּתְּפִין אֲלָפִים וּרְבָבוֹת שְׁתֵּי סְעֻדּוֹת לְכֻלָּן:
כסף משנה
9.
What quantity of food is necessary to establish a shituf? A measure equal to the size of a dried fig24As stated in Hilchot Shabbat 18:1, one is liable for t ransferring an amount of food equal to the size of a dried fig from one domain to another. Therefore, this is the size of the measure chosen to establish a shituf. (See Eruvin 80b.) for every inhabitant of the lane or of the city, provided there are eighteen or less. If, however, there are more than [eighteen inhabitants], the minimum measure [of the shituf] is [an amount of] food [sufficient] for two meals - i.e., an amount equivalent to eighteen dried figs, which is equivalent to the measure of six medium-size eggs.25According to Shiurei Torah, the size of an egg is 57.6 milliliters.; according to the Chazon Ish, it is 100 milliliters.
See also the Kessef Mishneh, who notes that based on Eruvin 82b-83a, there is an apparent contradiction between the Rambam's ruling here and his ruling in Hilchot Tum'at Ochalin 4:1. Nevertheless, a deeper analysis of the text in Eruvin allows for a resolution of both decisions.
Note also the Shulchan Aruch HaRav 368:3 which mentions an opinion that the measure is slightly less than the size of eight eggs. Since there are many halachic factors dependent on this measure, e.g., the measure of כדי אכילת פרס, the ruling is very significant.
Even if thousands and myriads of people desire to make use [of this shituf], [all that is necessary] is [an amount of] food [sufficient] for two meals.

הלכה י
כָּל אֹכֶל שֶׁהוּא נֶאֱכָל כְּמוֹת שֶׁהוּא כְּגוֹן פַּת וּמִינֵי דָּגָן וּבָשָׂר חַי אִם נִשְׁתַּתְּפוּ בּוֹ שִׁעוּרוֹ מְזוֹן שְׁתֵּי סְעֻדּוֹת. וְכָל שֶׁהוּא לִפְתָּן וְדֶרֶךְ הָעָם לֶאֱכל בּוֹ פִּתָּן כְּגוֹן יַיִן מְבֻשָּׁל וּבָשָׂר צָלִי וְחֹמֶץ וּמוּרְיָס וְזֵיתִים וְאִמָּהוֹת שֶׁל בְּצָלִים שִׁעוּרוֹ כְּדֵי לֶאֱכל בּוֹ שְׁתֵּי סְעֻדּוֹת:
כסף משנה
10.
When a shituf is made using any food that is eaten without further cooking - e.g., a loaf of bread, certain species of grain, or raw meat - the minimum measure is the [amount of] food [sufficient] for two meals.26The principle on which this halachah is based is expressed by Eruvin 29b: "For side dishes [that are eaten together with bread], the minimum measure is the amount [of these dishes] eaten at two meals. For food that is not a side dish, an amount large enough to eat two meals from it."
In Talmudic times, bread was the staple food that was generally served as the basis for a meal. Smaller quantities of other foods were also eaten at a meal, together with bread as "side dishes." Accordingly, if the food in question is usually eaten together with bread as a side dish, it is necessary to bring only the quantity that would usually be consumed as a side dish in a meal. If, however, the food is not usually eaten with bread, but instead is itself a staple that can be used as a staple instead of bread, the full amount necessary for two meals is required.

When the food in question is a side dish - i.e., something that people customarily eat together with bread - e.g., cooked wine, roasted meat, vinegar, fish brine, olives, and onion heads - the minimum measure is an amount sufficient to accompany two meals.27The Rambam gives several examples of the minimum amounts required for side dishes in the following halachah.

הלכה יא
נִשְׁתַּתְּפוּ בְּיַיִן חַי שִׁעוּרוֹ שְׁתֵּי רְבִיעִיּוֹת לְכֻלָּן. וְכֵן בְּשֵׁכָר שְׁתֵּי רְבִיעִיּוֹת. בֵּיצִים שְׁתַּיִם וּמִשְׁתַּתְּפִין בָּהֶן וַאֲפִלּוּ הֵן חַיּוֹת. וְרִמּוֹנִים שְׁנַיִם. אֶתְרוֹג אֶחָד. חֲמִשָּׁה אֱגוֹזִים. חֲמִשָּׁה אֲפַרְסֵקִים. לִיטְרָא שֶׁל יָרָק בֵּין חַי בֵּין שָׁלוּק וְאִם הָיָה בָּשִׁיל וְלֹא בָּשִׁיל אֵין מְעָרְבִין בּוֹ לְפִי שֶׁאֵינוֹ רָאוּי לַאֲכִילָה. עֻכְּלָא תַּבְלִין. קַב תְּמָרִים. קַב גְּרוֹגָרוֹת. מָנֶה דְּבֵלָה. קַב תַּפּוּחִין. כְּשׁוּת כִּמְלוֹא הַיָּד. פּוֹלִין לַחִין כִּמְלוֹא הַיָּד. חֲזִין לִיטְרָא. וְהַתְּרָדִין הֲרֵי הֵן בִּכְלַל הָיָּרָק וּמְעָרְבִין בָּהֶן. עֲלֵי בְּצָלִים אֵין מְעָרְבִין בָּהֶן. אֶלָּא אִם הִבְצִילוּ וְנַעֲשָׂה אֹרֶךְ כָּל עָלֶה מֵהֶן זֶרֶת. אֲבָל פָּחוֹת מִכָּאן אֵינוֹ אֹכֶל. וְכָל אֵלּוּ הַדְּבָרִים הָאֲמוּרִין כְּלִפְתָּן הֵן. וּלְפִיכָךְ נָתְנוּ בָּהֶן שִׁעוּרִין אֵלּוּ. וְכֵן כָּל כַּיּוֹצֵא בָּהֶן. וכָּל הָאֳכָלִין מִצְטָרְפִין לְשִׁעוּר הַשִּׁתּוּף:
כסף משנה
11.
When fresh wine28In contrast to the cooked wine mentioned in the previous halachah. is used for a shituf, two revi'iot are required for every [participant]. Similarly, if beer is used, two revi'iot [are required].
If eggs are used, [the minimum measure] is two; they may be used for a shituf even when raw. [Other minimum measures are:] two pomegranates,29See Hilchot Matnot Ani'im 6:8, which mentions this and several of the other measures cited by the Rambam in this halachah as "sufficient to satisfy" a poor man, and therefore fit to be given to him as "the tithe of the poor." Significantly, there it mentions "ten nuts," leading the Maggid Mishneh to consider amending the text here. one etrog, five nuts, five peaches, a Roman pound of vegetables - whether raw or cooked; if [the vegetables] are lightly, but not thoroughly, cooked, they may not be used;30Raw vegetables are eaten in salads, and cooked vegetables are eaten as foods, but partially cooked vegetables are not eaten at all. The Ra'avad maintains that this restriction applies only to beets, but the Maggid Mishneh explains that the same rationale - and therefore the same ruling - applies to other vegetables as well. an uchla31The Rambam defines this and several of the other measures he mentions in the following halachah. of spices, a kav of dates, a kav of dried figs, a maneh of crushed figs, a kav of apples, a handful of cuscuta,32A parasitic plant that grows on shrubs. a handful of fresh beans, a Roman pound of lichen.33A wild plant that is occasionally used for food. Some commentaries reverse the definitions of cuscuta and lichen.
Beets are considered vegetables and may be used for an eruv. Onion leaves may not be used for an eruv unless they are already grown, and the length of each leaf is at least that of a spread-out hand. If they are not this long, they are not considered to be food.34When the leaves grow long, they are called scallions and are edible. Before they grow long, however, they are bitter, and unfit to be used.
All these types of food are considered to be side dishes; therefore, they have been given these measures. The same principles apply in other similar situations. All foods can be combined to reach the minimum measure required for a shituf.35The Rambam's statements are based on the statements of the Mishnah (Me'ilah 4:7), which he interprets as referring to both an eruv t'chumim (an eruv to extend the Sabbath boundaries) and a shituf. The Ra'avad differs and maintains that the reference is only to an eruv t'chumim. Significantly, in his Commentary on the Mishnah (Me'ilah, loc. cit.), the Rambam mentions only an eruv t'chumim, seeming to imply that he originally held the same view as the Ra'avad. The Shulchan Aruch (Orach Chayim 386:4) follows the ruling of the Rambam in this halachah.

הלכה יב
לִיטְרָא הָאֲמוּרָה בְּכָל מָקוֹם מְלֹא שְׁתֵּי רְבִיעִיּוֹת. וְעֻכְּלָא חֲצִי רְבִיעִית. וּמָנֶה הָאֲמוּרָה בְּכָל מָקוֹם מֵאָה דִּינָר. וְהַדִּינָר שֵׁשׁ מָעִין. וְהַמָּעָה מִשְׁקַל שֵׁשׁ עֶשְׂרֵה שְׂעוֹרוֹת. וְהַסֶּלַע אַרְבָּעָה דִּינָרִין. וְהָרְבִיעִית מַחְזֶקֶת מִן הַמַּיִם אוֹ מִן הַיַּיִן מִשְׁקַל שִׁבְעָה עָשָׂר דִּינָרִין וַחֲצִי דִּינָר בְּקֵרוּב. נִמְצָא הַלִּיטְרָא מִשְׁקַל חֲמִשָּׁה וּשְׁלֹשִׁים דִּינָר. וְהָעֻכְּלָא מִשְׁקַל תִּשְׁעָה דִּינָרִין פָּחוֹת רְבִיעַ:
כסף משנה
12.
Whenever the term Roman pound is mentioned, it refers to [a measure equal to] two36Rashi differs and defines a Roman pound as equaling a log, four revi'iot. full revi'iot.37A revi'it, the measure on which all the other measures mentioned in this halachah is based, is 86.4 milliliters according to Shiurei Torah, and 150 milliliters according to the Chazon Ish. An uchla is half a revi'it; a maneh, one hundred dinarim; a dinar, six ma'ah; a ma'ah, the weight of sixteen barley corns;38See also Hilchot Shekalim 1:3. a sela, four dinarim.
A revi'it contains an amount of water or wine39Rav Moshe HaCohen objects to the Rambam's statements, because equal volumes of wine and water are not equal in weight. equivalent to approximately seventeen and one half dinarim. Thus, a Roman pound is equivalent in weight to 35 dinarim, and an uchla is equivalent in weight to eight and three-quarter dinarim.

הלכה יג
סְאָה הָאֲמוּרָה בְּכָל מָקוֹם שֵׁשֶׁת קַבִּין. וְהַקַּב אַרְבָּעָה לוֹגִין. וְהַלּוֹג אַרְבַּע רְבִיעִיּוֹת. וּכְבָר בֵּאַרְנוּ מִדַּת הָרְבִיעִית וּמִשְׁקָלָהּ. וְאֵלּוּ הַשִּׁעוּרִין שֶׁאָדָם צָרִיךְ לִזְכֹּר אוֹתָן תָּמִיד:
כסף משנה
13.
Whenever the term se'ah is mentioned, it refers to [a measure equal to] six kabbim. A kav is four logim, and a log is four revi'iot. We have already defined the measure and the weight of a revi'it.40In Hilchot Tefillah 15:4, the Rambam defines a revi'it as the volume of an area two fingerbreadths by two fingerbreadths, which is two and seven tenths of a fingerbreadth high. These measurements are necessary for a person to remember at all times.

הלכה יד
אֹכֶל שֶׁהוּא מֻתָּר בַּאֲכִילָה אַף עַל פִּי שֶׁהוּא אָסוּר לְזֶה הַמְעָרֵב הֲרֵי זֶה מְעָרֵב בּוֹ וּמִשְׁתַּתֵּף בּוֹ. כֵּיצַד. מִשְׁתַּתֵּף הַנָּזִיר בְּיַיִן וְיִשְׂרָאֵל בִּתְרוּמָה. וְכֵן הַנּוֹדֵר מֵאֹכֶל זֶה אוֹ שֶׁנִּשְׁבַּע שֶׁלֹּא יֹאכְלֶנּוּ מְעָרֵב בּוֹ וּמִשְׁתַּתֵּף בּוֹ. שֶׁאִם אֵינוֹ רָאוּי לָזֶה הֲרֵי הוּא רָאוּי לְאַחֵר:
כסף משנה
14.
[All] food that is permitted to be eaten, even if the person who uses it is forbidden to partake of it, may be used for an eruv41This refers to an eruv t'chumim, for, as stated in Halachah 8, an eruv for a courtyard may be established only with bread. or for a shituf.
What is implied? A nazirite42Who may not partake of wine (Numbers 6:3 . may establish a shituf using wine, and an Israelite [may establish a shituf using] terumah.43Although it may be eaten only by a priest (Leviticus 22:10, Numbers 18:12 .
Although this law is quoted by the Shulchan Aruch (Orach Chayim 386:8), Shulchan Aruch HaRav 386:8 and the Mishnah Berurah 386:47 note that in the present age, even the priests are ritually impure, and are therefore forbidden to partake of terumah. Hence, terumah may no longer be used for an eruv.
Similarly, a person who takes a vow or an oath not to partake44According to Rabbenu Asher and the Tur (Orach Chayim 386), the word "partake" is exact. Were a person to vow not to benefit from a food, he would be forbidden from using it for this purpose. (Others differ and maintain that since "the mitzvot were not given for our benefit," using the food for an eruv does not violate one's vow.) Shulchan Aruch HaRav, loc. cit., suggests that one should be stringent and follow the Tur's ruling. of a particular food may use it for an eruv or a shituf. For if it is not fit for one person [to partake of], it is fit for another.

הלכה טו
אֲבָל דָּבָר הָאָסוּר לַכּל כְּגוֹן טֶבֶל אֲפִלּוּ טֶבֶל שֶׁל דִּבְרֵי סוֹפְרִים. וְכֵן מַעֲשֵׂר רִאשׁוֹן שֶׁלֹּא נִטְּלָה תְּרוּמָתוֹ כַּהֹגֶן. וְכֵן מַעֲשֵׂר שֵׁנִי וְהֶקְדֵּשׁ שֶׁלֹּא נִפְדּוּ כַּהֲלָכָה. אֵין מְעָרְבִין וּמִשְׁתַּתְּפִין בָּהֶן. אֲבָל מְעָרְבִין וּמִשְׁתַּתְּפִין בִּדְמַאי מִפְּנֵי שֶׁרָאוּי לָעֲנִיִּים. וּבְמַעֲשֵׂר רִאשׁוֹן שֶׁנִּטְּלָה תְּרוּמָתוֹ. וּבְמַעֲשֵׂר שֵׁנִי וְהֶקְדֵּשׁ שֶׁנִּפְדּוּ אַף עַל פִּי שֶׁלֹּא נָתַן אֶת הַחֹמֶשׁ שֶׁאֵין הַחֹמֶשׁ מְעַכֵּב. וּמְעָרְבִין בְּמַעֲשֵׂר שֵׁנִי בִּירוּשָׁלַיִם מִפְּנֵי שֶׁהוּא רָאוּי שָׁם לַאֲכִילָה אֲבָל לֹא בִּגְבוּלִין:
כסף משנה
15.
A forbidden [food] - e.g., tevel,45Food from which terumah and the tithes have not been separated, and that is hence forbidden to be eaten. The Rambam's choice of foods is based on Berachot 7:1, which mentions that a blessing should not be recited when partaking of the foods mentioned in the first grouping, because they are forbidden. In contrast, a blessing should be recited over those in the second grouping. (See also Hilchot Berachot 1:19-20.) even food that is considered tevel only by Rabbinic decree46E.g., produce that grows in containers (Rambam's Commentary on the Mishnah, Berachot, loc. cit.)., the first tithe from which terumah was improperly taken,47This refers to an instance in which the first tithe was separated before terumah. Before it is permitted to partake of the tithe, it is necessary to separate terumah from it (ibid.). or the second tithe or consecrated articles that were not redeemed in the proper manner48The second tithe may be eaten only in Jerusalem, and consecrated a rticles may not be used for mundane purposes. These articles may be redeemed and then used for mundane purposes. In this instance, however, we are speaking about a situation where the redemption was improperly performed - e.g., one used uncoined metal (ibid.). - by contrast, may not be used for an eruv or a shituf.
We may, however, use d'mai49Produce from which we are unsure whether the tithes were separated or not. (See Hilchot Ma'aser 9:1.) for an eruv or a shituf, since it is fit to be used by the poor. Similarly, we may use the first tithe after terumah was removed, and the second tithe or consecrated articles that were redeemed, even if the [additional] fifth of their value was not paid.50When the second tithe or consecrated articles are being redeemed, it is necessary to add an additional fifth of the article's value. Nevertheless, once the value of the article itself is paid, even though the additional fifth is still outstanding, the article is considered redeemed and may be used for mundane purposes. (See Hilchot Ma'aser Sheni 5:12.) For [failure to give] the [additional] fifth does not [void the redemption of these articles].
We may use the second tithe in Jerusalem, since it is fit to be eaten there, but [it may] not [be used] outside [that city].

הלכה טז
כֵּיצַד מְעָרְבִין בַּחֲצֵרוֹת. גּוֹבִין חַלָּה אַחַת שְׁלֵמָה מִכָּל בַּיִת וּבַיִת וּמַנִּיחִין הַכּל בִּכְלִי אֶחָד בְּבַיִת אֶחָד מִבָּתֵּי הֶחָצֵר אֲפִלּוּ בְּבֵית הַתֶּבֶן אוֹ בְּבֵית הַבָּקָר אוֹ בְּבֵית הָאוֹצָר. אֲבָל אִם נָתְנוּ בְּבֵית שַׁעַר אֲפִלּוּ בֵּית שַׁעַר שֶׁל יָחִיד אוֹ בְּאַכְסַדְרָה אוֹ בְּמִרְפֶּסֶת אוֹ בְּבַיִת שֶׁאֵין בּוֹ אַרְבַּע אַמּוֹת עַל אַרְבַּע אַמּוֹת אֵינוֹ עֵרוּב. וּכְשֶׁמְּקַבֵּץ הָעֵרוּב מְבָרֵךְ בָּרוּךְ אַתָּה ה' אֱלֹהֵינוּ מֶלֶךְ הָעוֹלָם אֲשֶׁר קִדְּשָׁנוּ בְּמִצְוֹתָיו וְצִוָּנוּ עַל מִצְוַת עֵרוּב. וְאוֹמֵר בְּעֵרוּב זֶה יִהְיֶה מֻתָּר לְכָל בְּנֵי הֶחָצֵר לְהוֹצִיא וּלְהַכְנִיס מִבַּיִת לְבַיִת בְּשַׁבָּת. וְיֵשׁ לְקָטָן לִגְבּוֹת עֵרוּבֵי חֲצֵרוֹת. וּבַיִת שֶׁמַּנִּיחִין בּוֹ עֵרוּב אֵינוֹ צָרִיךְ לִתֵּן אֶת הַפַּת. וְאִם הָיוּ רְגִילִין לְהַנִּיחַ בּוֹ אֵין מְשַׁנִּין אוֹתוֹ מִפְּנֵי דַּרְכֵי שָׁלוֹם:
כסף משנה
16.
How is an eruv [joining the entire area of] a courtyard together established? We collect a complete loaf of bread from every house51The Ra'avad and Rav Moshe HaCohen differ with the Rambam and state that it was customary to collect a portion of flour from all the houses in the courtyard and then to bake a single loaf from it. Others mention the custom that one person would bake a loaf from his own flour and grant everyone a portion in it. (See Ramah, Orach Chayim 366:6.) and place all [the loaves] in a single container52See Halachah 18. in one of the houses of the courtyard.53The place where the eruv is stored must be fit to serve as a dwelling. All the examples that the Rambam mentions as acceptable can serve as a dwelling if necessary. By contrast, all those that he mentions as unacceptable are not fit to serve as a dwelling.
The Ramah (loc. cit.:3) states that since, at present, since a shituf is established for a larger area, it is unnecessary to be placed in a dwelling. For this reason, it is permitted - and this is indeed the custom - to place the eruvin in the synagogue.
Even a granary, a barn, or a storehouse [is acceptable for this purpose]. If, however, the eruv was placed in a gatehouse - even a gatehouse belonging to a private individual - an exedra,54A Greek architectural structure with two or three walls. a porch, or a house that is not four cubits by four cubits, it is not considered an eruv.
When the eruv is gathered together,55For the blessing should be recited before the mitzvah is carried out. The Beit Yosef (Orach Chayim 395) states that it is preferable to recite the blessing before one begins gathering the bread or the flour from each household. The later authorities, however, state that one may recite the blessing after completing the collection (Shulchan Aruch Harav 366:18; Mishnah Berurah 366:81). one recites the blessing: "Blessed be You, God, our Lord, King of the Universe, who has sanctified us with His commandments and commanded us56Even though the mitzvah of establishing an eruv was ordained by our Sages, it is proper to praise God when fulfilling His commandments, because carrying out the decrees of the Sages also fulfills God's commandments (Hilchot Berachot 11:3). concerning the mitzvah of the eruv." [Afterwards,] one says, "With this eruv, all the inhabitants of this courtyard will be permitted to bring objects in and out from one house to another."57The Shulchan Aruch (Orach Chayim 366:15) states that one should add "And from the courtyard to the houses and from the houses to the courtyard."
A minor may collect [the bread for] the eruv [joining the entire area of] a courtyard together. The house in which the eruv is placed need not give a loaf of bread.58Eruvin 49a explains that by having the loaf of bread they gave for the eruv located in a house, the other people who join in the eruv show that they have the right to dwell in that house. The person who actually dwells in the house where the eruv is kept, by contrast, does not need any further indication that it is his home. If [the inhabitants of a courtyard] ordinarily place [the eruv in one house], as an expression of "the ways of peace"59In his Commentary on the Mishnah (Gittin 5:8), the Rambam explains that since the person in whose home the eruv is kept benefits (for he does not have to contribute toward it), it is proper to continue offering him this benefit. The commentaries note that this interpretation appears to differ from that of the Talmud (Gittin 60b), which states that it should be kept in the original house because of "suspicion." (According to Rashi, this means the suspicion that will arise when people enter the house where the eruv is usually held, and see that there is no eruv there; according to Tosafot, it is intended to belie the suspicion that the place of the eruv was changed because the person in whose house it was kept stole from it.) it is proper that they should not change [to another home].

הלכה יז
וְכֵיצַד מִשְׁתַּתְּפִין בְּמָבוֹי. גּוֹבֶה אֹכֶל כִּגְרוֹגֶרֶת מִכָּל אֶחָד וְאֶחָד אוֹ פָּחוֹת מִכִּגְרוֹגֶרֶת אִם הָיוּ מְרֻבִּין. וּמַנִּיחַ הַכּל בִּכְלִי אֶחָד בְּחָצֵר מֵחַצְרוֹת הַמָּבוֹי אוֹ בְּבַיִת מִן הַבָּתִּים אֲפִלּוּ בַּיִת קָטָן אוֹ אַכְסַדְרָה אוֹ מִרְפֶּסֶת הֲרֵי זֶה שִׁתּוּף. אֲבָל אִם הִנִּיחוֹ בַּאֲוִיר מָבוֹי אֵינוֹ שִׁתּוּף. וְאִם הִנִּיחַ הַכְּלִי בֶּחָצֵר צָרִיךְ לְהַגְבִּיהַּ הַכְּלִי מִן הַקַּרְקַע טֶפַח כְּדֵי שֶׁיִּהְיֶה נִכָּר. וּמְבָרֵךְ עַל מִצְוַת עֵרוּב. וְאוֹמֵר בְּזֶה הַשִּׁתּוּף יִהְיֶה מֻתָּר לְכָל בְּנֵי הַמָּבוֹי לְהוֹצִיא וּלְהַכְנִיס מֵחֲצֵרוֹת לַמָּבוֹי בְּשַׁבָּת:
כסף משנה
17.
How is a shituf established for a lane? We collect [an amount of food] equivalent to the size of a dried fig from each and every person - or less than this amount,60See Halachah 9. if many people are involved. The entire amount is placed in a single container in one of the courtyards in the lane, or in one of the homes. [It is even acceptable] to place it in a small home, in an exedra, or in a porch. If, however, one leaves it in the open space of the lane, it is not acceptable.61I.e., the governing principle is that the shituf must be kept in a protected place. A courtyard is acceptable for this purpose, because it is the private property of the inhabitants of the houses that adjoin it. The lane itself, however, is public property, and therefore unacceptable.
If one leaves the container in one of the courtyards, one must lift the container at least a handbreadth above the ground of the courtyard, so that it will be obvious.62The Maggid Mishneh quotes geonim who agree with the Rambam, but also other authorities who state that lifting up the container is necessary only when the container belongs to another person and he is granting the inhabitants of the lane the right to use it. To manifest their acquisition, they are required to lift it up a handbreadth above the ground.
In the Kessef Mishneh, Rav Yosef Karo explains that, according to the Rambam, it makes no difference if the container is held in a courtyard or in a home; it should always be lifted a handbreadth above the ground so that it will be obvious. Nevertheless, in the Shulchan Aruch (Orach Chayim 386:9), Rav Karo quotes the other opinion mentioned by the Maggid Mishneh.
[When making the shituf,] one recites the blessing, "... concerning the mitzvah of the eruv,"63One may use the term eruv, which means "joining," since a shituf also involves a joining together of all the courtyards in the lane (Mishnah Berurah 395:2). Even when one fails to recite the blessing, the shituf is still effective (Ramah, Orach Chayim 395:1). and says, "With this shituf, it will be permitted for all the inhabitants of this lane to bring objects in and out - from the lane to the courtyard and from the courtyard to the lane - on the Sabbath."64The Ramah (loc. cit.) states that one should also add "from the courtyards to the houses" in this statement. (See Halachah 19 and notes.)

הלכה יח
חָלְקוּ אֶת הָעֵרוּב אוֹ אֶת הַשִּׁתּוּף אַף עַל פִּי שֶׁהוּא בְּבַיִת אֶחָד אֵינוֹ עֵרוּב. אֲבָל אִם מִלְּאוּ אֶת הַכְּלִי מִן הָעֵרוּב וְנִשְׁאַר מִמֶּנּוּ מְעַט וְהִנִּיחוּהוּ בִּכְלִי אַחֵר מֻתָּר:
כסף משנה
18.
If one divides the eruv or the shituf, it is no longer effective. [This ruling applies] even if [all the portions of the eruv] are located in a single home. If, however, one fills a container with the eruv and there remains some food that one put in a second container, it is acceptable.65The Maggid Mishneh explains that both these containers must be located in the same house. This stipulation is quoted by the Shulchan Aruch (Orach Chayim 366:4).
Commenting on this ruling, the Mishnah Berurah notes that when a shituf is made for an entire community, it should be placed in one synagogue. It is not proper to divide it and place a portion in each of the community's synagogues.

הלכה יט
הַמִּשְׁתַּתְּפִין בַּמָּבוֹי צְרִיכִים לְעָרֵב בַּחֲצֵרוֹת כְּדֵי שֶׁלֹּא יִשְׁכְּחוּ הַתִּינוֹקוֹת תּוֹרַת עֵרוּב. שֶׁהֲרֵי אֵין הַתִּינוֹקוֹת מַכִּירִין מַה נַּעֲשָׂה בַּמָּבוֹי. לְפִיכָךְ אִם נִשְׁתַּתְּפוּ בַּמָּבוֹי בְּפַת סוֹמְכִין עָלָיו וְאֵין צְרִיכִין לְעָרֵב בַּחֲצֵרוֹת שֶׁהֲרֵי הַתִּינוֹקוֹת מַכִּירִין בַּפַּת. בְּנֵי חֲבוּרָה שֶׁהָיוּ מְסֻבִּין וְקָדַּשׁ עֲלֵיהֶן הַיּוֹם פַּת שֶׁעַל הַשֻּׁלְחָן סוֹמְכִין עָלֶיהָ מִשּׁוּם עֵרוּבֵי חֲצֵרוֹת. וְאִם רָצוּ לִסְמֹךְ עָלֶיהָ מִשּׁוּם שִׁתּוּף סוֹמְכִין אַף עַל פִּי שֶׁהֵן מְסֻבִּין בֶּחָצֵר:
כסף משנה
19.
The participants in a shituf in a lane must, nevertheless, also make an eruv in their [respective] courtyards, so that their children will not forget the laws of an eruv.66Although a lane is a private domain according to the Torah, and one might therefore assume that a single shituf would be sufficient, Eruvin 71b requires that the inhabitants of the courtyards establish eruvin. Otherwise, it is possible that their children will grow up and carry in a courtyard without establishing either a shituf or an eruv because of their ignorance of the matter.For this reason, if bread67The bread must be a whole loaf, and it must be placed within a house. Otherwise, it is unacceptable for use as an eruv (Mishnah Berurah 387:6).
It is customary to use bread (more particularly, matzah) as a shituf and to place the shituf for the entire community in the synagogue. This creates a slight difficulty, because a synagogue may not be used as a dwelling. The Ramah (366:3, 387:1) uses this as support for his thesis that at present, once a shituf is made, there is no need for the courtyards to make eruvin. (See also Chapter 5, Halachot 13-14.)
is used as a shituf in a lane, [the inhabitants] may rely on it, and are not required to make an eruv for the courtyards, for the children will take notice of the bread.68Since bread is the staple of our diet, it will be noticed by the children (Beit Yosef, Orach Chayim 387).
If a group of people were participating in a feast together, and the Sabbath commenced, they may rely on the bread on the table before them as an eruv for the courtyard.69Provided they are eating within a house (Shulchan Aruch, Orach Chayim 366:11). If they desire to rely on this bread as a shituf for a lane,70The Maggid Mishneh states that this law applies regardless o f whether the food was owned mutually, or belonged to one person. For, as stated in the following halachah, a person may grant others a portion in his food, and establish an eruv or a shituf on this basis. they may, even though they are dining in a courtyard.

הלכה כ
לָקַח אֶחָד מִבְּנֵי הֶחָצֵר פַּת אַחַת וְאָמַר הֲרֵי זוֹ לְכָל בְּנֵי הֶחָצֵר אוֹ שֶׁהוּא אֹכֶל כִּשְׁתֵּי סְעֻדּוֹת וְאָמַר הֲרֵי זֶה לְכָל בְּנֵי הַמָּבוֹי אֵינוֹ צָרִיךְ לִגְבּוֹת מִכָּל אֶחָד וְאֶחָד. אֲבָל צָרִיךְ לְזַכּוֹת לָהֶן בּוֹ עַל יְדֵי אַחֵר. וְיֵשׁ לוֹ לְזַכּוֹת עַל יְדֵי בְּנוֹ וּבִתּוֹ הַגְּדוֹלִים וְעַל יְדֵי עַבְדּוֹ הָעִבְרִי וְעַל יְדֵי אִשְׁתּוֹ. אֲבָל לֹא עַל יְדֵי בְּנוֹ וּבִתּוֹ הַקְּטַנִּים וְלֹא עַל יְדֵי עַבְדּוֹ וְשִׁפְחָתוֹ הַכְּנַעֲנִים מִפְּנֵי שֶׁיָּדָן כְּיָדוֹ. וְכֵן יֵשׁ לוֹ לְזַכּוֹת לָהֶן עַל יְדֵי שִׁפְחָתוֹ הָעִבְרִית אַף עַל פִּי שֶׁהִיא קְטַנָּה. שֶׁהַקָּטָן זוֹכֶה לַאֲחֵרִים בְּדָבָר שֶׁהוּא מִדִּבְרֵי סוֹפְרִים. וְאֵינוֹ צָרִיךְ לְהוֹדִיעַ לִבְנֵי הֶחָצֵר אוֹ לִבְנֵי הַמָּבוֹי שֶׁהֲרֵי זָכָה לָהֶן וְעֵרֵב עֲלֵיהֶן שֶׁזְּכוּת הִיא לָהֶן וְזָכִין לוֹ לְאָדָם שֶׁלֹּא בְּפָנָיו:
כסף משנה
20.
[A person may establish an eruv on behalf of others. For example,] if one of the inhabitants of a courtyard takes bread and says, "Behold, this is for all the inhabitants of the courtyard," or he took an amount of food equivalent to two meals, and says, "This is for all the inhabitants of the lane," he does not have to collect food from each individual. He must, however, [give their portion] to another person,71In the Kessef Mishneh, Rav Yosef Karo mentions opinions that require the person who receives the food on behalf of the inhabitants of the courtyard or the lane to live there himself, as well. He, however, appears to reject this view and does not mention it in the Shulchan Aruch. who will acquire it on their behalf.72I.e., the person gives the bread or the food to the recipient and asks him to take possession of it on behalf of all the inhabitants of the courtyard or the lane. Afterwards, since they have a share in the food, it is considered as though they had contributed toward the eruv.
One's son or daughter who has reached majority,73In this ruling, the Rambam follows the simple interpretation of the Mishnah (Eruvin 7:6). Tosafot (Eruvin 79b) differs and interprets the words קטנים and גדולים in terms of financial dependence. קטנים refers to children dependent on their parents even if they are past the age of majority. גדולים refers to children independent of their parents even if they are below the age of majority.
The Shulchan Aruch (Orach Chayim 366:10) states that at the outset, it is desirable to satisfy both views. After the fact, as the Ramah states explicitly, as long as a person made an eruv in accordance with either of these opinions, it is acceptable.
one's Hebrew servant,74Because the financial status of a Hebrew servant is independent of that of his master. and one's wife may take possession on behalf of others. Neither a son nor a daughter below the age of majority, nor a Canaanite servant or maidservant has this prerogative, because they do not have independent financial status.75The Hebrew term for this expression (quoted by the Rambam from Eruvin, loc. cit.) is ידם כידו - literally, "their hand is like his hand." Since they have no independent financial status, it is as if the article has never left the possession of its original owner.
Similarly, a Hebrew maidservant may take possession on behalf of others, even though she is below the age of majority,76Although she is a minor, her status differs from that of the owner's children, because she is not at home. for a minor may take possession on behalf of others regarding a matter of Rabbinic law.
A person need not inform the inhabitants of a lane or a courtyard that he has granted them [a portion of food] and established an eruv for them, for these deeds are to their benefit, and a person may grant a colleague benefit without the latter's knowledge.77This principle applies in several different financial contexts. If a person takes possession of an article on behalf of a colleague, it becomes the latter's property even though he himself is unaware of the transaction. (See also Chapter 5, Halachot 4 and 23.)

הלכה כא
אֵין מְעָרְבִין וְלֹא מִשְׁתַּתְּפִין בְּשַׁבָּת אֶלָּא מִבְּעוֹד יוֹם. וּמְעָרְבִין עֵרוּבֵי חֲצֵרוֹת וְשִׁתּוּפֵי מְבוֹאוֹת בֵּין הַשְּׁמָשׁוֹת אַף עַל פִּי שֶׁהוּא סָפֵק מִן הַיּוֹם סָפֵק מִן הַלַּיְלָה. וּלְעוֹלָם צָרִיךְ שֶׁיְּהֵא הָעֵרוּב אוֹ הַשִּׁתּוּף מָצוּי וְאֶפְשָׁר לְאָכְלוֹ כָּל בֵּין הַשְּׁמָשׁוֹת. לְפִיכָךְ אִם נָפַל עָלָיו גַּל אוֹ אָבַד אוֹ נִשְׂרַף אוֹ שֶׁהָיָה תְּרוּמָה וְנִטְמֵאת מִבְּעוֹד יוֹם אֵינוֹ עֵרוּב. מִשֶּׁחֲשֵׁכָה הֲרֵי זֶה עֵרוּב. וְאִם סָפֵק הֲרֵי זֶה עֵרוּב שֶׁסְּפֵק הָעֵרוּב כָּשֵׁר:
כסף משנה
21.
Neither an eruv nor a shituf may be established on the Sabbath. Instead, they must be established before nightfall. One may, however, establish an eruv for a courtyard78An eruv extending one's Sabbath boundaries, by contrast, s hould be established before sunset. (See Chapter 6, Halachah 13.) and a shituf for a lane beyn hash'mashot,79The time between sunset and the appearance of three stars. even though there is a doubt whether that time period is considered to be part of the day or part of the night.
The eruv and the shituf must always be accessible, so that one may partake of it throughout the time of beyn hash'mashot.80See Chapter 6, Halachah 14. For this reason, if, before nightfall, an avalanche fell upon it, it was lost or burned, or it was terumah and became impure, it is not considered to be an eruv. If the above took place after nightfall, the eruv is acceptable. If one is in doubt when this took place, the eruv is acceptable, because whenever a doubt arises whether an eruv is acceptable or not, it is considered acceptable.81Since the requirement to establish an eruv is a Rabbinic institution, we follow the principle: Whenever a doubt arises regarding a question of Rabbinic law, the more lenient option is followed.

הלכה כב
נָתַן הָעֵרוּב אוֹ הַשִּׁתּוּף בַּמִּגְדָּל וְנָעַל עָלָיו וְאָבַד הַמַּפְתֵּחַ קֹדֶם שֶׁחֲשֵׁכָה אִם אִי אֶפְשָׁר לוֹ לְהוֹצִיא הָעֵרוּב אֶלָּא אִם כֵּן עָשָׂה מְלָאכָה בֵּין הַשְּׁמָשׁוֹת הֲרֵי זֶה כְּמִי שֶׁאָבַד וְאֵינוֹ עֵרוּב שֶׁהֲרֵי אִי אֶפְשָׁר לְאָכְלוֹ. הִפְרִישׁ תְּרוּמַת מַעֲשֵׂר אוֹ תְּרוּמָה גְּדוֹלָה וְהִתְנָה עָלֶיהָ שֶׁלֹּא תִּהְיֶה תְּרוּמָה עַד שֶׁתֶּחְשַׁךְ אֵין מְעָרְבִין בָּהּ שֶׁעֲדַיִן הִיא טֶבֶל כָּל בֵּין הַשְּׁמָשׁוֹת וְצָרִיךְ שֶׁתִּהְיֶה סְעֻדָּה הָרְאוּיָה מִבְּעוֹד יוֹם:
כסף משנה
22.
[The following rules apply when] an eruv or a shituf was placed in a tower, [the tower] was locked, and the key was lost before nightfall: If it is impossible to remove the eruv without performing [a forbidden] labor82This refers to a labor forbidden by the Torah itself. If the act is forbidden merely by Rabbinic law, the eruv is acceptable, for a sh'vut is not forbidden beyn hash'mashot (Maggid Mishneh). (See Chapter 6, Halachah 10, and Hilchot Shabbat 24:10.) beyn hash'mashot, it is considered as if it had been lost. Therefore, the eruv is not acceptable, for it is impossible for it to be eaten.
If a person separated terumat ma'aser83The tenth of the tithe, which the Levites must give to the priests. or terumah, and made a stipulation that the sacred status not be conveyed [upon these entities] until nightfall, they may not be used for an eruv. [The reason is that] beyn hash'mashot, they are still tevel,84I.e., it is as if the terumah or the terumat ma'aser had not been separated at all. (See also Chapter 6, Halachah 16.) and [the food used for an eruv must be fit to be eaten before nightfall.

זמנים הלכות עירובין פרק א
Zemanim Eruvin Chapter 1